Pacificabathynella ruthae, Camacho & Newell & Reid, 2009
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publication ID |
https://doi.org/ 10.1080/00222930903015832 |
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persistent identifier |
https://treatment.plazi.org/id/3C3587A4-FF94-FFB8-FE1D-D10F75F7FC43 |
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treatment provided by |
Felipe |
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scientific name |
Pacificabathynella ruthae |
| status |
sp. nov. |
Pacificabathynella ruthae sp. nov.
( Figures 6 View Figure 6 to 8)
Material examined
Type locality. Flathead County, Middle Fork Flathead River , 2 February 2004, Wally ER, Chris B, HA-12, Wally C wells (six males and two females), Montana, USA; other locality: Flathead County, Great Bear well, 9 November, 2003 (one male and four females), Montana, USA (see Table 1). The details of the new description are based on all 13 specimens. The holotype is a male and the allotype is a female and the type series contains 11 additional specimens (six males and five females). (Holotype MNCN20.04 About MNCN /8096, allotype MNCN20.04 About MNCN /8097 and type series MNCN20.04 About MNCN /8098.)
Description
Body. Total length of holotype (male) 1.94 mm and allotype (female) 1.68 mm. Largest male total length 2.07 mm, smallest 1.57 mm; largest female total length 1.78 mm, smallest 1.45 mm (see Table 4). Body form not very elongated, almost cylindrical, approximately 13 times long as wide. Pleotelson with one barbed dorsal seta on either side, shorter than furcal rami.
Antennule ( Figure 6A View Figure 6 ). Seven segments; length of first three segments similar to the other four segments; segments five and six similar in size and smaller than other segments; setulation as in Figure 6A View Figure 6 ; three aesthetascs on segments six and seven. A.I almost equal in length to A.II.
Antenna ( Figure 6B View Figure 6 ). First four segments longer than terminal three; three terminal segments of similar length; setal formula: 0/2+exp/2+0/2+0/0+0/2+2/5; ventromedial seta of exopod absent, two terminal setae, one a bifurcated sensory seta.
Labrum ( Figure 6C View Figure 6 ). With median protusion.
Paragnath ( Figure 6D View Figure 6 ). Large, subrectangular, with one tooth on distal part and with very thick setulation on entire surface of distal half.
Mandible ( Figure 6E–G View Figure 6 ). Palp with three segments, terminal segment with two barbed similar claws, second segment more or less rectangular. Incisor process (pars incisiva) with two teeth; processus incisivus accessorius with one tooth, and one long seta-like tooth; pars molaris with two dentated structures ( Figure 6F,G View Figure 6 ) parallel to main axis of teeth, first with four similar teeth, other with small similar teeth arranged in two rows, crown-like, most distal tooth is strong and longer than others.
Maxillule ( Figure 6H View Figure 6 ). Proximal endite with four setae; distal endite with six teeth, four with spines (denticles), other two setae-like, with three plumose setae.
Maxilla ( Figure 6I View Figure 6 ). Four segments; setal formula 7, 4, 7, 5.
Thoracopods I to VII ( Figure 7A–H View Figure 7 ). Sexual dimorphism Th. VI, ( Figure 7F,H View Figure 7 ). Th. I ( Figure 7A View Figure 7 ) lightly smaller than others; Th. II ( Figure 7B View Figure 7 ) to V ( Figure 8B View Figure 8 ) similar in size to Th. VII ( Figure 7G View Figure 7 ) and longer than others. Th. I and II without epipod; coxa of Th. I with long, strong plumose seta, basipod with three setae, one of these plumose. Exopod one- segment for all thoracopods, shorter than endopod in all cases; with six barbed setae, two terminal, one dorsal and three ventral. Endopod with four segments in all thoracopods, setal formulae (number of setae of basipod in brackets):
Th. I: (3) 6+0/5+1/5+0/5
Th. II: (4) 4+0/4+1/4+0/5
Th. III: (4) 3+0/3+1/2+0/5
Th. IV: (3) 2+0/3+1/2+0/4
Th. V: (1) 2+0/2+1/2+0/4
Th. VI: (1) 1+0/0+1/2(1)
Th. VII: (1) 1+0/0+1/0+0/2(1)
Thoracopod VI ( Figure 7F View Figure 7 ) with only three segments in endopod: first segment broader than usual, second segment broad-dilated, bearing on its outer margin strong medially curved seta and third segment small with two setae, one long and another short. Basipods of Th. I and Th. VII have tufts of long and fine setules.
Male thoracopod VIII ( Figure 8A–C View Figure 8 ). Longitudinal axis of coxa and basipod form angle of 25°. Penial region with frontal lobe, inner lobe, outer lobe. Frontal lobe with two very well-developed lobules that cover outer lobe and partially cover inner lobe. Well-developed inner lobe has distal region elongated with very large bidentated projection on internal side. Outer lobe similar to frontal lobe and with two almost square lobules. Basipod very large, with distal crest-like protuberance, three rows of setules distally on inner side, two smooth setae, one distal-lateral and another on external side. Endopod one-segmented, small, 33% of the exopod, with only one barbed distal seta. Exopod well developed with six setae.
First pleopods ( Figure 8D View Figure 8 ). Two segments, first segment with one very long seta; second segment with six setae.
Female thoracopod VIII allotype ( Figure 8G View Figure 8 ). Coxa with one, small, barbed lateral seta; very large epipod, twice length of basipod; basipod almost square, longer than endopod, with smooth seta; endopod one-segmented, with one smooth seta; exopod a little longer than endopod and with two apical smooth setae of similar length.
Female thoracopod VI allotype ( Figure 7H View Figure 7 ). Exopod one segmented and with six setae, as in other thoracopods; endopod four-segmented, setal formula 1+0/0+1/0+0/ 2(1). Number of setae on segments of endopod and on basipod of thoracopods is different on female. Setal formulae of allotype (number of setae of basipod in brackets):
Th. I: (3) 6+0/6+1/6+0/5
Th. II: (5) 5+0/5+1/4+0/5
Th. III: (4) 3+0/3+1/3+0/5
Th. IV: (4) 3+0/3+1/3+0/5
Th. V: (4) 3+0/3+1/3+0/5
Th. VI: (1) 1+0/0+1/0+0/2(1)
Th. VII: (1) 1+0/0+1/0+0/2(1)
Uropods ( Figure 8E View Figure 8 ). Sympod a little longer than endopod, almost twice as long as wide, with six equal spines on distal end; endopod 10% longer than exopod, with six strong claws, two most distal longest, twice length of penultimate, three times length of two most basal, with two very long terminal setae and with two shorter ones located dorsolaterally, all of which barbed; exopod with nine setae, two terminal, four medial, three basal.
Furcal rami ( Figure 8F View Figure 8 ). Almost square, bearing five spines; a long dorsal spine, almost half length of second spine, second spine 30% longer than two equal length medial spines, medial spines 25% times longer than fifth.
Variability
The variability is very low between individuals and populations.
The observed variability only affects the numbers of setae on the different segments of the endopods of thoracopods I to V in males and females (see Table 5), which differ from the holotype and allotype as follows :
Males:
Th. I: 6+0/5–6+1/5–6+0/5
Th. II: 4+0/4+1/4+0/5
Th. III: 3+0/3+1/2–3+0/5
Th. IV: 2+0/2–3+1/2–3+0/4–5
Th. V: 2+0/2–3+1/2+0/4
Females:
Th. I: (3) 5–6+0/5–6+1/5–6+0/5
Th. II: (5) 4–5+0/4–5+1/3–4+0/5
Th. III: (4) 3+0/3+1/3+0/5
Th. IV: (4) 3+0/3+1/3+0/5
Th. V: (4) 2–3+0/2–3+1/2–3+0/5
Etymology
The species name is derived from Ruth Dalimata, wife of John Dalimata, who owns the land surrounding the Nyack well sites and has long been supportive of the research occurring on this large floodplain.
Remarks
Pacificabathynella ruthae sp. nov. is the largest known species of the genus (see Table 4); the largest specimens reach 2 mm. This is the only species of the genus in which the antennule is similar in length to the antenna. The female thoracopod VIII has the smallest epipod within the genus. Despite being the largest species of the genus it does not have more setae on thoracopods (see Table 5) and uropods (see Table 3) than other species. The endopod of the uropod has six spines (the others species have four, five or eight), the exopod has nine setae, while other species have only seven or eight setae.
The species that share the greatest number of similar characters are P. stanfordi .sp. nov. and P. sequoiae . Pacificabathynella stanfordi sp. nov. differs principally in the number of setae on the exopod of the thoracopods, having six (see Table 5), which is the norm in the genus, and the male thoracopod VIII is very different from that of the other species.
| VI |
Mykotektet, National Veterinary Institute |
| V |
Royal British Columbia Museum - Herbarium |
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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